He'd have to wear size 145 shoes for a start!
“Spiders and ants can do it. So, why can’t I?” This unspoken lament must be firmly entrenched in our psyche judging from the huge industry built around the cartoon idol Spiderman with blockbuster films, toys swept off the counters, masks, suits and what not.
Yet, according to a study by researchers from Cambridge University, the fantasy is bound to remain a fantasy. The size limit for animals that possess this ability is that of the gecko. Animals with larger body sizes would need uncontrollably big feet with sticky pads to be able to climb up walls.
Findings of the study published in the Proceedings of the National Academy of Sciences (PNAS) show that for humans to be able to walk on walls or ceilings, they would have to be equipped with sticky pads covering an area corresponding to 40 percent of their body surface, or 80 percent of their fronts.
And that means having feet which require size 145 shoes (US size 114)!
Dr. David Labonte of the Zoology Department of Cambridge University explains the limit nature has imposed on the ability to walk on straight walls or inverted surfaces:
“As animals increase in size, the amount of body surface area per volume decreases – an ant has a lot of surface area and very little volume, and a blue whale is mostly volume with not much surface area” explains Labonte.
As the size and masses of species increase, they need bigger sticking power but they lack adequate surface area for sticky pads. So, the ceiling set by nature for the animals to walk upside down is the size of a gecko, Labonte concludes.
For the study, researchers compared masses and footpad sizes of 225 animals including insects, frogs, spiders, lizards and a mammal displaying the ability to climb.
The fact that animals of very diverse species and body sizes have taken different evolutionary paths to arrive at the same solution for the ability to climb is a striking example of convergent evolution, Labonte notes.
As for animals that can still climb up walls despite an insufficient footpad size, the solution has been making their feet “stickier”.
Researchers point out that study of such evolutionary solutions may help development of large scale artificial adhesive pads.
- 1. “Why Spiderman can’t exists: Geckos are ‘size limit’ for sticking to walls”, University of Cambridge, 18 January 2016